TH LEX 1
SH NAME
lex \- generator of lexical analysis programs
SH SYNOPSIS
B lex
[
B -tvn
]
[
I file ...
]
SH DESCRIPTION
I Lex
generates programs to be used in simple lexical analysis of text.
The input
I files
(standard input default)
contain regular expressions
to be searched for and actions written in C to be executed when
expressions are found.
PP
A C source program,
B lex.yy.c
is generated.
This program, when run, copies unrecognized portions of
the input to the output,
and executes the associated
C action for each regular expression that is recognized.
PP
The options have the following meanings.
TP
B -t
Place the result on the standard output instead of in file
BR lex.yy.c .
TP
B -v
Print a one-line summary of statistics of the generated analyzer.
TP
B -n
Opposite of
BR -v ;
B -n
is default.
SH EXAMPLES
This program converts upper case to lower,
removes blanks at the end of lines,
and replaces multiple blanks by single blanks.
PP
EX
%%
[A-Z]   putchar(yytext[0]+\'a\'-\'A\');
[ ]+$
[ ]+    putchar(\' \');
EE
SH FILES
TF /sys/lib/lex/ncform
TP
B lex.yy.c
output
TP
B /sys/lib/lex/ncform
template
SH "SEE ALSO"
IR yacc (1),
IR sed (1)
br
M. E. Lesk and E. Schmidt,
`LEX\(emLexical Analyzer Generator',
I
Unix Research System Programmer's Manual,
Tenth Edition, Volume 2.
SH SOURCE
B /sys/src/cmd/lex
SH BUGS
Cannot handle
SM UTF.
br
The asteroid to kill this dinosaur is still in orbit.

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